Thermal simulation and system optimization of a chilled ceiling coupled with a floor containing a phase change material (PCM)

The integration of phase change materials (PCMs) for cooling applications in buildings reduces the amplitude of indoor air temperature fluctuations due to solar and internal gains, enabling passive solar, HVAC system downsizing or off-peak cooling designs. This work studies the use of radiant systems for discharging heat stored in a PCM; this approach differs from the typical practice of accomplishing this task by either night cooling ventilation or embedding an active heat exchanger into the PCM of the wall. In this study, a PCM is incorporated into the floor, and a hydronic radiant ceiling system is used as the energy discharge system. The advantages and disadvantages of this configuration in terms of cooling energy demands and thermal comforts of occupants are analyzed using the simulation software TRNSYS®. Five design parameters are optimized using the software GENOPT®. The simulation reveals that when accompanied by an air-to-air heat recovery system, this configuration can significantly reduce the cooling energy demand (more than 50% compared to the cooling energy demand of the same building without PCM) and can thus significantly reduce the energy consumption. However, the degrees of occupant comfort will inevitably vary (i.e., the predicted percent dissatisfied (PPD) increases by 2-5%).